Childhood Attention Deficit Hyperactivity Disorder (ADHD) is among the most common reasons for referral to medical, psychological, and school services. Even in the absence of co-morbid learning disabilities, children with ADHD are at high risk for academic underachievement. Adolescent and adult outcome studies indicate that children with attention problems are not only more likely to access special education services and tutoring, but also have a higher high school drop-out rate and lower occupational status. Therefore, determining how the learning process proceeds in children with ADHD, and what neuropsychological factors may impact skill acquisition, is crucial to both theory development and clinical application. The proposed study will examine the role working memory plays in the development of complex cognitive and sensorimotor skills in children with the combined (ADHD-C) and primarily inattentive (ADHD-I) subtypes of ADHD. Children from the local community will be recruited from schools, newspaper ads, and distributed flyers. To obtain as broadly a representative sample as possible, they will also be recruited from local pediatric, psychological, and psychiatric clinics. ADHD and co-morbid diagnoses will be made according to DSM-IV criteria and will be based on parent/teacher questionnaires as well as a structured interview administered to parents. Children will complete computer-generated tasks designed to measure the process of skill acquisition, along with standard neuropsychological measures of working memory, academic achievement, and cognitive functioning. The proposed cognitive neuroscience approach to understanding ADHD has the potential to better inform a mechanistic model of ADHD subtypes. Specifically, this approach will help identify whether and how established neuropsychological deficits (namely, deficits in working memory) may directly impact the process of learning, and thus lead to academic underachievement. If this process can be illuminated, such findings may eventually lead to the development of better academic remedial programs and treatments. [unreadable] [unreadable] [unreadable]